Method of preparing 16-ketosteroids



Patented Apr. 21, 1953 Max N. Huffman, Oklahoma, City, Qkla,, assigiiorto G. D. Searle & 00., Chicago, Ill;, a corporation of Illinois NoDrawing"; Appncationniisust 31, 1951, Serial No. 244,713

18 Claims. (01. etc-#3914) This invention pertains to the conversion ofm-ketols to ketones. More specifically, it relates to the synthesis ofIG-ketosteroids having a 16,17- dihydro 15Hcyclopenta[alpolyhydrophenanthrene nucleus. Particularly this inventionrelates to the removal of a l7--hydroxy group by the treatment with zincand acid of a steroid with the following structure in ring D is reducedwith zinc and acid, there occurs the unexpected formation of thecorresponding 16- keto l'l-desoxycompound.

I have now found that this method is one of general applicability andcan be applied to e-ketols of all types. Itis of particular interest forthe removal of a l'l-hydroxy groupin the formation of lfl-lzetosteroidswith difierent types of nuclear unsaturation andeven in the productiorlof the fully saturated l,2,3,4,5,6,7,8,9,10,11,12,13,14,16,17-hexadecahydro 15H cyclopentalalphenanthrenes.

The reductions are generally carried out in an organic solvent suitablefor Clemrnensen reductions. Water-soluble solvents such as methanol,ethanol, propanol, isopropanol, and dioxane are suitable as are waterins'oluble solvents" such as benzene, toluene, and otherhydrocarbons'boiling in the range of 50 150 0. The reactions aregenerally conducted at temperatures in the range' of 50-l50 C. overperiods of about 3' to 10 hours. Generally concentrated hydrochloricacid is used in the reductions, but acid as dilute as 5% and asconcentrated as 40% may be used. The form of the zinc is not critical.It is preferably amalgamated by reaction with its Weight of a-5-10%mercuric chloride solution in very dilute hydrochloric acid.

The lG-ketosteroidscan generally be obtained from the reaction medium byBxtractiqnwith an organic solvent and removal of the impurities bywashing with water, dilute alkali and dilute acid, followed byevaporation of the organic solventto yieldthe desired substances,generally in a crystalline form. If the product thus obtained is not fin rp es eton c e n erted to such adducts as semicarbazones, oximes,arylh s r zp s t m n a eteh dr enesand r l e? 2i n ee T s adduets are ten pur f ledand hydrolyzed to theoriginal ketones by an agent such as adilute acid. v p u g It will be recognized that the reaction conditionsdescribed herein correspond to those of a mild Clemmensen reduction,(cf. Organic Reactions, volume 1, page 155 et seq., 1942). How-- ever,while the typical Clemmensen reductions operate to change a ketone groupto a methylene group, I have now found; that, unless the reaction iscarried too far, it functions as an effective method for the removal ofan a-hydroxyl radical fro rna; hetol 'Ifhis process makes availablebye..,vi*e iie Synth c: met o a b e he i a intermediates and compoundsofmedicinal value. 'l'he method is applicable to steroid nuclei of variousdegrees ofsaturation. 0 Thus it can be u th ln e ti o l re il non wh chhas} a r'iaphthalene structurein ringsn' and B, s i l c b fir qen i et qwh ch a a cempletely saturated nucleus, It-is of rade-a1: imma e t ih let e p ie ae me o selectiye removal of thel'l-hydrogcy group fromsteroids which contain hydroxy groupsin ether positions" of thefiucieus. The, process is likewise applicable to thelfi-ketd-l6,17-dihydro-l5H- cyclopenta a] polyhydrophenanthrenescontainingsuch nuclear substituents in rings A, B and C as lowerhydrocarbon, ether and ester substitni a a I M nve ion wil appear e llfr m t following experimental part. It will be understood, however, thatthese examples are set forth wayof illustration only and that theinvention not to be" construed as limited spirit or in scope'fbyj'th'edetails contained therein. ,Itfwill be apparent to those skilled in theart'th'at many modifications in materials and methods can" as madewithout departing from the scope of the invention. In the followingexamples, temperatures" are given uncorrected-in degrees centigrade(Chi, and quantities in grams (g), milligrams (mg), and milliliters(ml.)-.

Eadmziled 693 milligrams of lfi-keto-a-estradlolare dissolvedin 45 ml;ofethanol containing a mi.

solution is refluxed gently for 2 hours.

' w'ater'. rated, yielding a crystalline white residue of -A-estratrien-3-ol-16-one. This material recrystallized from aqueousmethanol using acti- 'vated charcoal and gives tiny fine white needlestion). methanol raises the melting point to 2435-2455 C. (withdecomposition).

'ously for minutes.

'pe'rature for several hours.

3 of 6 N hydrochloric acid. To this solution is added amalgamated zinc(prepared from g. of -mesh zinc) and the resulting mixture is refluxedfor 5 hours, with the addition of 3 ml. portion of 6 N hydrochloric acidat each 15- minute interval. At the end of 3 hours of refluxing, 11 ml.of ethanol are added. At the end of the 5-hour period the mixture iscooled, treated with 750 ml. of ether and 700 ml. of water. The etherlayer is separated, washed with water, with 3% sodium bicarbonatesolution, and then twice with water. The solution is dried andevaporated, yielding a White crystalline residue, which is treated with0.60 g. of semicarbazide hydrochloric acid and 0.84 g. of crystallinesodium acetate in 36 m1. of ethanol and 4 ml. of water.

The mixture is refluxed for one hour and then ml. of water are added. Onchilling and standing for two days the crystalline semicarbazone isremoved by filtration, washed copiously with water, and recrystallizedfrom hot methanol. The purified crystalline semicarbazone of jA-estratrien-3ol-16-one is removed by filtration, washed with 50%methanol and with water, and dried. The product so obtained melts at2445-2 17" 0. Further recrystallization from 95% ethanol and from amixture of chloroform and absolute ethanol and then twice from absoluteethanol, gives material melting with decomposition at 2465-248" C.

Example 2 v 220 mg. of the semicarbazone of A -estratrien-3-ol-16-oneare dissolved in 75 ml. of ethanol and 25 ml. of 2 N hydrochloric acid.The Then 5 ml. of pyruvic acid in 20 m1. of water are added to the hotsolution with thorough mixing. The resulting solution is left for about15 hours at room temperature. It is then diluted with ether and theethereal solution is washed with water,

with dilute hydrochloric acid, twice with 5% sodium carbonate solutionand finally twice with The ether solution is dried and evapowhich meltat 2425-2435 C. (with decomposi- Further recrystallization from absoluteExample 3 37 mgof A -estratrien-B-ol-16-one dissolved in ml. of warm N/2sodium hydroxide solution are cooled and treated with 0.50 ml. ofbenzoyl chloride, and the mixture is shaken vigor- After 24 hours atroom temperature the benzoate is removed by filtration, washed well withWater, and dried. 0n recrystallization from a mixture of acetone andethanol jfine needles of A -estratrien-3-o1-16-one ben- 'zoa-temeltingat 2235-2245 C. (with slight decomposition) are obtained.

Example 4 48 mg. of A -estratrien-3-ol-16-one in 1 ml.

'of dry pyridine are treated with 1 ml. of acetic anhydride. Thereaction mixture is kept at room temperature for 24 hours withoccasional agitation. It is then diluted with 50 ml. of ice cold water,thoroughly mixed and left at room tem- The crude acetate whichprecipitates is removed by filtration,

,ide and 200 ml. of ether. is thoroughly agitated and the ether layer issep- Example 5 53 mg. of A -estratrien-3-ol-16-one in dry pyridine isreacted with 0.50 ml. of palmitoyl chloride. A white thick precipitateforms at once with the evolution of heat. The reaction mixture isdiluted further with 1.5 m1. of dry pyridine and agitated continuouslyfor 15 minutes. Then 0.25 ml. of water is added. The mixture is agitatedfor an additional 5 minutes and then diluted with 40-50 ml. of coldwater. After 24 hours at room temperature the precipitate of A-estratrien-3- ol-16-one palmitate containing some palmitic acid isremoved by filtration. washed well with water, and dried in vacuum.Several recrystallizations from ethanol afford the crystalline A-estratrien-3-ol-l6-one palmitate as waxy plates melting at 110.5111.50.

Example 6 50 mg of A -estratrien-3-ol-16-one are covered with a solutionof 4 g. of potassium hydroxide in 9 ml. of water. The mixture isagitated, cooled, and treated with 1 ml. of methanol. It is then heatedon the steam bath, treated with 1 m1. of dimethyl sulfate and, after thereaction subsides, with an additional 1 ml. of dimethyl sulfate. Themixture is refluxed for 15 minutes and then 5 ml. of water are added.After 24 hours standing at room temperature the precipitate of the crudemethyl ether of A -estratrien-3-ol- 16-one is removed by filtration,washed thoroughly with water, and then recrystalized from aqueousacetone using decolorizing charcoal. A second crystallization fromaqueous methanol gives plates of the 3-methoxy-A -estratrien-lG-onemelting at 124-125" C. Further recrystallization from 80 methanol givescolorless plates melting sharply at 124-1245 C.

Example 7 50 mg. of A -estratrien-3-ol-16-one are covered with 113 mg.of anhydrous potassium carbonate and then 0.10 ml. of benzyl chloride in2.5 ml. of ethanol'added. The mixture is refluxed on the steam bath for1.5 hours and then 0.6 ml. of water added. The mixture is chilled andthe precipitate of the benzyl ether of A estratrien-B-ol-lfi-one iscollected on a filter after a day in the refrigerator, washed with cold75% ethanol, and then with water and dried.

The 3-benzyloxy-ri -estratrien-l6-one is then recrystallized severaltimes from 95% ethanol and forms silky needles melting at 156-1565 0.

Example 8 To 179 mg. of A -estratrlen-3-ol-16-one benzoate are added 500mg. of anhydrous sodium sulfate and 250 mg. of freshly fused zincchloride. The. mixture is covered at once with 10 ml. of ethylmercaptan. The flask is stoppered and the mixture is thoroughlyagitated. The benzoate soon dissolves with a development of a, pinkcolor.

After 3 days standing in the refrigerator the mixture is evaporatedunder vacuum at 30 C. in order to remove excess mercaptan. The residueis treated with 200 ml. of 1 N sodium hydrox- The resulting mixturearated, and washed twice with water containing a trace of pyridine. Theether solution is then dried and to it are added 1 m1. of pyridine, ml.

of absolute ethanol, and ml. of benzene. The resulting solution isevaporated to a volume of a fewml. on the steam bath. The resulting oilyExample 9 To the oily thioacetal of Example 8 are added 3 g. of Raneynickel catalyst (saturated with hydrogen) and 30 m1. of absolutealcohol. The

mixture is refluxed for 7 hours on the steam bath, cooled, and filteredto remove catalyst.

To the filtrate are added 30 ml. of 2 N potassium hydroxide and thealkaline solution is refluxed for minutes. The resulting solution isevaporated to remove a portion of the alcohol. The

remaining alkaline solution is acidified with. di-

lute hydrochloric acid and then taken up in ether. The ether solution iswashed with water, twice with 3% sodium carbonate solution and finallytwice with water. The ether solution is dried and evaporated, yieldingan oil which soon crystallizes. The crystalline material is treated withcarboxymethoxylamine to remove any ketom'c material. The resultingnon-ketonic fraction is crystallized twice from aqueous ethanol to give77 mg. of desoxoestrone melting at 133-134 C. This material did notdepress the melting point of authentic desoxoestrone.

39 mg. of the desoxoestrone obtained above are dissolved in 2 m1. of drypyridine and treated with 0.5 ml. of benzoyl chloride. There is obtainedin this manner long needles of the crystalline desoxoestrone benzoatewhich melt at 169- 169.5 0., after recrystallization from a mixture ofacetone and methanol. This product did not depress the melting point ofauthentic desoxoestrone benzoate.

Example 10 A solution of 4.25 g. of potassium in 175 m1. of drytert-butanol is added to 4 g. of l'l-isoandroster-one(SIB-hydroxy-androstan-ll-one). To the resulting solution an initialportion of 4 ml. of isoamyl nitrite is added and, after stirring for 2.5hours, an additional portion of 3.0 ml. 01

amyl nitrite. Stirring is continued for 2.5 hours longer after which themixture is treated with 1000 ml. of ice water and 1750 ml. of ether.Then 750 ml. of glycine hydrochloride (containing 85 g. of glycine and38 ml. of concentrated hydrochloric acid) are added and the mixture isat once partitioned. The ether layer is separated and washed with 1000ml. of 3% sodium bicarbonate and the nitroso compound is extracted usingN/2 potassium hydroxide. The alkaline extract is rendered acid byaddition of concentrated hydrochloric acid and left standing for 12hours. A precipitate forms which is collected on a filter, Washedcopiously with water and dried in a vacuum. The16-oximino-1'l-lsoandrosterone thus obtained melts at about 213-215 C.with decomposition. A sample, recrystallized from methanol, sinteredslightly at about 212 0., browned at 215.5 C. and decomposed with gasformation at about 213-2195 C.

3.505 g. of 1B-oximinoisoandrosterone are cov- -'eredwith 232 ml. ofacetic acid, treated with 9.3 g. of zinc dust and refluxed for '75minutes. After cooling to room temperature the solution is decanted fromthe zinc and the zinc is rinsed twice with 15 ml. of acetic acid. Thefiltrates are diluted with 131 ml. of water and stored at 0 C. Theresulting precipitate is washed with Water, dissolved in 350 ml. of hotmethanol and 200 ml. of Water. This solution is distilled and the 35.17dihydroxyandrostan 16- one crystallized in the hot. The precipiate iscollected on a filter, washed well with water and dried, whereupon itmelts at about 208.5-210 C. Upon repeated recrystallization from 50%methanol colorless crystals are obtained which melt sharply at 217-218C. and turn yellow on melting.

Example 11 0.902 g. of 35,17-dihydroxyandrostan-iii-one melting at about210-212 (3., are dissolved in ml. of ethanol. To this solution.amalgamated zinc is added, prepared from 23 g. of 20-mesh zinc, 2.3 gLofmercuric chloride, 45- ml. of water and 3.1 ml. of 6 N hydrochloricacid. The mixture is heated at reflux temperature on a water bath for 30minutes and then for an additional 5 hours with the addition of 4.5 ml.portions of 6 N hydrochloric acid at each 15- minute interval. Aftercooling the mixture is added to 800 ml. of 0.25 N hydrochloric acid and800 ml. of benzene. The benzene layer is separated and washed twice with500 ml. of 1 N sodium hydroxide and twice with 500 ml. of water. Thebenzene solution is then evaporated, the residue, is taken up inmethanol and the methanol solution evaporated.

To the residue are added 10 g. of trimethylaminoacetohydrazidehydrochloride (Girards reagent T), 10 m1. of glacial acetic acid and 90ml. of absolute ethanol. The mixture is heated at reflux temperature onthe steam bath for 1 hour, moisture being excluded by use of a calciumchloride tube. After chilling at 0 C. the mixture is added to 800 ml. ofice water and 6 g. sodium hydroxide and extracted at once with 800 ml.of ether. The ether phase, being non-ketonic, is discarded.

The aqueous phase, containing the trimethylaminoacetohydrazone oflfi-isoandrosterone is hydrolyzed with 62 ml. of concentratedhydrochloric acid, left standing for 12 hours and then extracted with800 ml. of ether. This ether extract is washed successively with water,1 N sodium hydroxide and Water. The ether solution is then evaporatedand the residue is recrystallized repeatedly from 50% methanol andfinally from a mixture of acetone and petroleum ether. Thelfi-isoandrosterone thus obtained melts at about 186-186.5 O. and hasthe structural formula on; on.

Example 1.2

appears which is separated and dried in a vacuum. Upon repeatedrecrystallizations from acetone and from ethanol, small feathery needlesof Sfi-benzoyloxy-androstan-lG-one are obtained which melt at 208.5-209C.

Example 13 A mixture of 46 mg. of 16-isoandrosterone, 100 mg. ofcrystalline sodium acetate, 50 mg. of hydroxylamine hydrochloride, 4.5ml. of 95% ethanol and 0.5 ml. of water is heated gently on the steambath for 2 hours and then stored at C. The precipitated oxime iscollected on a filter and washed well with water. It melts at about198.5-199.5 C. with slight decomposition. Upon recrystallization fromdilute methanol and decolorization with charcoal, fine White needles areobtained which melt sharply at about 199 C. Without decomposition.

Example 14 530 mg. of 3-benzy1oxy-A -estratrien-17- ol16-one, melting atISIS-198 C., are dissolved in a solution of 1.3 ml. or 6 N hydrochloricacid in 30 ml. of 95% ethanol. To this solution is added zinc amalgamprepared from 10 g. of 20- mesh zinc and the resulting mixture isrefluxed for hours with the addition of 2 m1. portions of 6 Nhydrochloric acid at each 15-minute interval. At the end of 2 hours ml.of ethanol are added. After completion of the addition of thehydrochloric acid the mixture is cooled, treated with 500 ml. of etherand 500 ml. of water. The ether layer is separated and washed first withwater, then with 3% sodium bicarbonate solution, and then again withWater. Upon drying and evaporation a white crystalline residue isobtained.

To this residue are added '7 g. of trimethylaminoacetohydrazidehydrochloride in 7 ml. of glacial acetic acid and 60 ml. of absoluteethanol and the mixture is refluxed for an hour with exclusion ofmoisture. After cooling the reaction product is poured into a solutionof 4 g. of sodium hydroxide in 500 ml. of ice water and then extractedwith 500 ml. of ether.

The aqueous solution of the trimethylaminoacetohydrazone of3-benzyloxy-A -estratrien- 16-0ne is hydrolyzed with hydrochloric acidand the hydrolysate extracted with ether. The ether extract is washedwith water, dilute sodium hydroxide and again with water and finallyevaporated. Upon repeated recrystallization from 95% ethanol the3-benzyloxy-A -estratrien- 16-one is obtained in the form of colorlesscrystalsmelting at about 1-156 C.

Example 15 A solution of 1 g. of 3B, 17-dihydroxy-A androsten-16-one in100 ml. of ethanol is treated with zinc amalgam prepared from g. ofzinc, 2.5 g. of mercuric chloride, 50 ml. of water and 3.4 ml. of 6 Nhydrochloric acid. The resulting mixture is heated at reflux temperaturefor minutes and then for an additional 5 hours with the addition of 5ml. portions of 6 N hydrochloric acid at 15-minute intervals. Thereaction product is cooled and treated with 1 liter of hydrochloric acidand 1 liter of benzene. The benzene layer is separated and washed with lN potassium hydroxide and water and finally evaporated. The residue istaken up in methanol and upon evaporation of the methanol, whitecrystals are obtained. Purification by way of thetrimethylaminoacetohydrazone yields pure 35-A -androsten-16-one.

This same process is likewise applicable to the conversion of17-hydroxyequilen 16 one to equilen-lS-one and of3.17-dihydroxyequilen-l6- one to 3-hydroxy-equilen-16-one.

I claim:

1. The process of producing a IS-ketosteroid containing a16,1'7-dihydro-15I-I-cyclopenta-[a] polyhydrophenanthrene nucleus whichcomprises treatment of the 17-hydroxy derivative of such a16-ket0steroid with zinc and acid to remove the 17-hydroxy group.

2. The process of producing a l6-ketosteroid containing a16,1'7-dihydro-15I-I-cyclopenta-[a] polyhydrophenanthrene nucleus whichcomprises treatment of the l7-hydroxy derivative of such alfi-ketosteroid with zinc and hydrochloric acid to remove the 17-hydroxygroup.

3. The process of producing a lfi-ketosteroid containing an androstanenucleus which comprises treatment of a l7-hydroxy derivative of such a16-ketosteroid with zinc and hydrochloric acid to remove the IT-hydroxygroup.

4. The process of preparing a l6-keto-androstane containing in the3-position a monovalent oxygen-function of the type --OR, wherein R is amember of the class consisting of hydrogen, lower acyl and lowerhydrocarbon, which comprises treatment of the 17-hydroxy derivative ofsuch a 16-ketosteroid with zinc and hydrochloric acid to remove the17-hydr0xy group.

5. The process of preparing a 3-hydroxy-l6- keto-androstane whichcomprises reacting 2. 3,17 dihydroxy 16 keto androstane with zinc andhydrochloric acid.

6. The process of preparing a 3fl-hydroxy-16- keto-androstane whichcomprises reacting 2. 33,17 dihydroxy l6 keto androstane with zinc andhydrochloric acid.

7. The process of preparing a 3p-hydroxy-l6- keto-androstane whichcomprises reacting a 3,3,17 dihydroxy l6 keto androstane withamalgamated zinc and hydrochloric acid.

8. The process of producing a 16-ketosteroid containing a A -estratriennucleus which comprises treatment of a l7-hydroxy derivative of such alS-ketosteroid with zinc and hydrochloric acid to remove the 17-hydroxygroup.

9. The process of preparing a l6-keto-A estratrien containing in the3-position a monovalent oxygen-function of the type -0R, wherein R is amember of the class consisting of hydrogen, lower acyl and lowerhydrocarbon, which comprises treatment of the l7-hydroxy derivative ofsuch a l6-ketosteroid with zinc and hydrochloric acid to remove thel7-hydroxy group.

10. The process of producing a lfi-ketosteroid of the formula wherein Ris a member of the group consisting of hydrogen and lower hydrocarbonradicals,

which comprises reacting a 16-keto-l7-hydroxysteroid of the formula withzinc and hydrochloric acid and separating the 16-ketosteroid thusformed.

11. The process of claim 10 wherein R represents hydrogen.

12. The process of claim 11 wherein the zinc is amalgamated zinc.

13. The process of claim 12 wherein the reaction is conducted in aqueousalcohol.

14. The process of claim 13 wherein the 16- ketosteroid is separated bymeans of its semicarbazone.

15. The process of claim 14 wherein the starting material is16-keto-a-estradiol.

16. The process of producing n -estratrien- 3-ol-16-one which comprisesreacting l6-ketoa-estradiol with zinc amalgam and hydrochloric acid inaqueous alcohol at reflux temperature, separating the steroidalmaterial, reacting said steroidal material with semicarbazide in aqueousalcohol, separating the crystalline semicarbazone of A-estratrien-3-ol-16-one, hydrolyzing said semicarbazone, and isolatingthe A -estratrien- 3-ol-16-one.

17. The process of producing a 16-ketosteroid containing a A-dehydroandrostane nucleus which comprises treatment of a 17-hydroxyderivative of such a 16-ketosteroid with zinc and hydrochloric acid toremove the 17-hydroxy group.

18. The process of producing a 16-ketosteroid containing an equileninnucleus which comprises treatment of a I'I-hydroxy derivative of such a.lfi-ketosteroid with zinc and hydrochloric acid to remove the1'7-hydroxy group.

MAX N. HUFFMAN.

No references cited.

1. THE PROCESS OF PRODUCING A 16-KETOSTEROID CONTAINING A16,17-DIHYDRO-15H-CYCLOPENTA-(A) POLYHYDROPHENANTHRENE NUCLEUS WHICHCOMPRISES TREATMENT OF THE 17-HYDROXY DERIVATIVE OF SUCH A16-KETOSTEROID WITH ZINC AND ACID TO REMOVE THE 17-HYDROXY GROUP.